TC4钛合金低磷化学镀工艺研究

针对TC4钛合金低磷化学镀,在浸锌活化和乳酸-乙酸络合条件下,对镍磷质量浓度比、温度、pH值、乙酸、乳酸等工艺因素对镀速和镀层磷含量的影响进行系列实验研究。用扫描电镜、能谱仪、显微硬度仪、X射线衍射仪对镀层的表面形貌、硬度和物相进行表征。研究结果表明：提高镍磷质量浓度比、温度、pH值,控制络合剂乳酸在20g/L～22g/L,乙酸在19g/L～20g/L范围内,均有利于低磷镀层的形成,平均镀速为25.6μm/h;镀层为晶态的Ni-P过饱和固溶体,平均粒径10μm,磷含量为2.56wt%,硬度为750.2HV.

Technology Research on Low-phosphorus Electroless Plating of Titanium Alloy TC4

Low-phosphorus electroless nickel plating was carried out on titanium alloy TC4 by using activated zincate treatment and lactic-acetic complex system.The effects of process parameters such as concentration ratio of NiSO4·6H2O to NaH2PO2·H2O,temperature,pH,acetic acid and lactic acid on the deposition rate and phosphorus content of the electroless Ni-P coating were studied.The morphology,elemental composition,hardness,and phases in the coating layer of TC4 were investigated by scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,microhardness testing machine and X-ray diffraction（XRD）,respectively.The results revealed that it is conducive to the formation of low-phosphorus coating by increasing the concentration ratio of NiSO4·6H2O to NaH2PO2·H2O,temperature and pH,while,the amounts of complexing agent which was controlled within a certain range（lactic acid 20g/L～22g/L,acetic acid 19g/L～20g/L）does favor to form a low-phosphorus coating.Moreover,the results of SEM/EDS investigations and X-ray diffraction indicated that the coating was crystalline Ni-P supersaturated solid solution with average grain diameter 10μm and phosphorus content 2.56wt%.The average deposited rate was 25.6μm/h and microhardness of the as-deposited coating was 750.2HV.